The subject matter of the present invention is new copolymers useful as adhesion mediating agents and having at least two fundamental constituents which have two chain carbon atoms, one of the fundamental constituents containing an alkoxysilyl group. Also subject matter of the present invention is copolymers which occur in the production of these new polymeric adhesion mediating agents ("adhesivizers") and a method for the preparation of the new polymeric adhesivizers from these new copolymers which occur as intermediate products.
German Pat. No. OS 2,624,888 has already disclosed copolymers in which one of the fundamental constituents with two chain carbon atoms contains an alkoxysilyl group which is directly linked to the fundamental constituent. Ihe additional ethylenically unsaturated fundamental component having two chain carbon atoms, however, is attached to only one acid group or acid anhydride group or ester group. These compounds are not suitable for use directly as adhesivizers between polymers and inorganic oxide material. They produce an appreciable adhesivizing action only when they are used in mixtures with organofunctional silanes.
It is furthermore known, for example through German Pat. No. 1,270,716, that organofunctional alkoxysilyl compounds containing an acrylic or methacrylic group as a functional group, have good adhesive ability between fillers and polymers. The use of these compounds as adhesivizers, however, is limited by the fact that the methacrylate component in the molecule is present in a relatively high concentration, so that these compounds, if uniformly distributed in the polymer-and-filler mixture that is to be bonded, are often used in an excessively great concentration. In many cases the strength of adhesion to the polymer would be just as well promoted or increased by a lower concentration of acrylate groups with respect to the alkoxysilyl groups.
The object of the invention therefore was:
(a) to make available a new class of adhesivizing agents containing both acrylate or methacrylate groups and alkoxysilyl groups, in which the concentration of acrylate or methacrylate groups and alkoxysilyl groups can be varied absolutely or relative to one another over a wide range, and which PA1 (b) will have at least as good an adhesivizing action as the silanes of German Pat. No. 1,270,716. Another object was to discover a method of preparing such adhesivizing agents.
For the achievement of this object, copolymers have been discovered which contain at least two different fundamental constituents, each containing two chain carbon atoms, and one of these constituents being attached to an alkoxysilyl group. They are characterized in that one fundamental constituent contains an alpha-halogen carboxylic acid moiety whose halogen atom can be replaced in some cases by an acrylic or methacrylic acid moiety, and in that, in the case of the second fundamental constituent, the alkoxysilyl moiety is connected to the fundamental constituent either directly or through a group ##STR1##
A process has furthermore been found for the preparation of those copolymers, in which one of the fundamental constituents contains an acrylic or methacrylic acid moiety. This process is characterized in that copolymers of the invention having fundamental constituents with two chain carbon atoms each, in which one constituent is linked with an alpha-halogen carboxylic acid moiety, are reacted with an alkali or alkaline earth salt of acrylic or methacrylic acid.
Copolymers of the invention, in which one of the fundamental constituents is linked to an acrylic or methacrylic acid moiety, prove to have an excellent adhesivizing action between inorganic oxide materials and polymers. This action occurs not only when the fundamental constituent having the acrylic or methacrylic acid moiety is present in the polymer in an amount of as little as 0.5 wt.-%, but also when it is present in amounts of as much as 99.5 wt.-%. All values between these are possible.
It is therefore possible in accordance with the invention for the new copolymers to contain additional, known fundamental constituents having two chain carbon atoms which do not contain any acrylic or methacrylic acid moiety nor any alkoxysilyl moiety. Such additional fundamental constituents can be in the polymer in such a maximum amount that the percentage of the fundamental constituents which do have alkoxysilyl and (meth)acrylate groups amounts in each case to at least 0.5% by weight.
The fundamental constituents containing the alphahalogen carboxylic acid moiety are derived from alpha-chloro or alpha-bromo fatty acid vinyl esters. The fatty acid moiety is preferably one having two or three carbon atoms, although higher fatty acids of up to 18 carbon atoms can be used. Preferred monomers are the alpha-chloro or alpha-bromo acetic acid vinyl esters.
The fundamental constituents containing an alkoxysilyl group are, on the one hand, the same as those contained in the compounds of German Pat. No. OS 2,624,888. Additionally, however, in these constituents the alkoxysilyl moiety can be linked to these constituents by a ##STR2## group to one of the carbon atoms of the fundamental constituent, as for example in the case of gamma-methacryloxypropyltrimethoxysilane. Examples of monomers from which these basic constituents are formed are the vinyltrialkoxysilanes whose alkoxy groups have preferably up to 4 carbon atoms, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyl-tris-(2-methoxyethoxy)-silane and gamma-methacryloxypropyltrimethoxysilane.
The additional basic constituents that may be contained in some cases in the copolymers of the invention, and which contain neither an acrylate or methacrylate nor an alkoxysilyl group, are derived from monomers which are copolymerizable with the ethylenically unsaturated monomer containing the alkoxysilyl group as well as with an ethylenically unsaturated monomer containing the alpha-halogen carboxylic acid moiety, examples being vinyl acetate, vinyl propionate, vinyl laurate, vinyl stearate, diethylmaleinate, diethyl fumarate, maleic acid anhydride, ethyl acrylate and methyl methacrylate. These groupings, also referred to herein as nonfunctional basic constituents, can be characterized by the following formulas: ##STR3## wherein R represents hydrogen, methyl or ethyl, R.sup.1 hydrogen or a C.sub.1 to C.sub.18 alkyl moiety, and R.sup.2 hydrogen or a C.sub.1 to C.sub.4 alkyl moiety. The person skilled in the art will be familiar with suitable nonfunctionalized vinyl monomers as starting products for the corresponding fundamental constituents in the copolymers.
The copolymers of the invention can furthermore contain, if desired, in addition to or instead of the copolymerized nonfunctionalized monomers, up to 99% by weight of an additional functionalized monomer which makes a polymer soluble or emulsifiable in water, examples being N-vinylpyrrolidone, methylvinyl ether, N-vinylmorpholinone-3, N-vinyl- 1,3-oxazidinone-2, or ethylenically unsaturated compounds which are capable of later forming salts with acids or bases through functional groups, but do not react with the alkoxysilyl group or the halogen function or the acrylate or methacrylate function, examples being maleic acid anhydride, itaconic acid anhydride, and 2-diethylaminoethylacrylate or -methacrylate.
The ethylenically unsaturated monomers on which the fundamental constituents are based can easily be copolymerized by known free-radical methods. The initiators used for the polymerization are compounds known for the purpose, such as organic peroxides or azoisobutyric acid dinitriles, for example. The following are given as examples: benzoyl peroxide, diacetyl peroxide, methylethylketone peroxide, methylisobutylketone peroxide, cyclohexanone peroxide, cymene hydroperoxide, tert.-butylhydroperoxide, di-tert.-butylperoxide, dicumyl peroxide, 1,3-di-tert.-butylperoxyisopropylbenzene, tert.-butylperacetate, tert.-butylperoctoate, tert.-butylperpivalate, tert.-butylisononanate. The catalyst is added in amounts of 0.2 to 3 percent of the weight of the ethylenically unsaturated monomer, which usually suffices for the achievement of a reasonable rate of reaction and a high monomer transformation.
The polymerization to the copolymers of the invention, in which the carboxylic acid moiety attached to the basic constituent is substituted in .alpha.-position by halogen, can be performed in substance, i.e., without the use of a diluent or solvent. Preferably, however, it is a polymerization in solution. Those solvents can be used which in no way interfere with the polymerization or react with the alkoxysilyl group or the halogen-carboxylic acid moiety of the vinyl monomers. Suitable solvents are fatty acid esters, such as for example acetic acid ethyl ester, ketones such as acetone or methyl ethyl ketone or aromatic hydrocarbons, such as for example benzene or toluene. The ratio of vinyl monomers and solvents can amount to between 4:1 and 1:4 by weight.
The said copolymerization is generally performed by placing all the monomers together in the reaction vessel and causing them to react randomly according to their relative concentrations and relative reactivities, so that random polymers are formed. To increase or reduce the inhomogeneity of the polymers, however, one or more of the ethylenically unsaturated monomers can be fed in gradually in the course of the polymerization. It is furthermore also possible to perform the polymerization as a graft copolymerization in which up to 3 of the ethylenically unsaturated monomers corresponding to the fundamental constituents are grafted in a known manner onto a previously formed polymer that contains the rest of the fundamental constituents to be contained in the copolymers of the invention. The nature of these reactions is generally known in the field of free-radical polymerization.
The preparation of the polymers which can act as adhesivizers, and in which a fundamental constituent is attached to a functional acrylic or methacrylic group, is performed by a reaction of alkali or alkaline earth salts of acrylic or methacrylic acid, and copolymers in which one of the fundamental constituents is attached to a halogencarboxylic acid moiety. The alkali acrylates or methacrylates are used in such amounts that, for each gram atom of chlorine in the starting copolymer, 1 to 1.5 gram molecules of the acrylates or methacrylates are available. Preferably this ratio amounts to 1:1.1.
A preferred embodiment of the reaction consists in the use of solutions of the above-named starting copolymers as produced, for example, in the solution polymerization performed for the preparation of the copolymers of the invention having fundamental constituents containing the halogen carboxylic acid moiety. The solvent used in this case, however, can also be replaced entirely or partially, after the polymerization, by another solvent suitable for the reaction.
On account of the peculiar reactivity of the alkoxysilyl group in the corresponding fundamental units, the selection of suitable solvents is greatly limited. In the majority of cases the solubility of the alkali acrylates and methacrylates in the usable solvents is low. This has a disadvantageous effect on the rate of reaction, which therefore is generally very slow.
In further development of the present invention, this disadvantage is overcome by performing the reaction with the acrylates in the presence of phase transfer catalysts. Examples of suitable phase transfer catalysts are crown ethers or especially quaternary ammonium or phosphonium salts, such as tetrabutyl ammonium chloride, tetrabutyl ammonium bromide, tetraphenyl phosphonium bromide, trimethylbenzyl ammonium bromide, methyltricaprylyl ammonium chloride. Examples of usable crown ethers are 12-crown-4, 24-crown-8, dibenzo-18-crownether-6. Additional usable crown ethers and ammonium or phosphonium salts are known to the chemist from the literature.
The polymer solutions used in the reaction with the alkali acrylates and methacrylates can contain residual amounts of the initiator used in their preparation. The presence of these initiators can lead to difficulties in the reaction with the alkali acrylates if the polymer constituents containing acrylate or methacrylate are provoked to intramolecular crosslinking reactions with the formation of three-dimensional networks. This intramolecular crosslinking, however, is to be prevented insofar as possible in the preparation of these polymers.
In the production of the adhesivizers of the invention, it is therefore advantageous to make the residual initiators contained in the starting polymers ineffective. This is accomplished in accordance with the invention by heating these polymer solutions prior to the reaction with the alkali or alkaline earth acrylates and methacrylates until the initiators are completely destroyed, at temperatures above the decomposition temperature of the radical-forming substances. The initiators can also be made ineffectual by the addition of stabilizers which act as polymerization inhibitors, such as for example di-tert.-butyl cresol, hydroquinone monomethyl ether, phenol, pyrogallol, hydroquinone or phenothiazine.
The person skilled in the art will be familiar with other suitable stabilizers. If these stabilizers are used in an amount of about 0.01 to 3% of the weight of the polymer, they inhibit the intramolecular crosslinking of the polymeric adhesivizer during its manufacture, its application and its storage.
The reaction with the acrylates or methacrylates need not be complete. It will suffice for the reaction to progress to the extent that the polymer obtained contains at least 0.5% by weight of fundamental constituents to which the methacrylic group is attached.
The copolymers obtained by this reaction act as adhesivizers between polymers and fillers, pigments or dyes. The polymers in question are any which can be modified by free-radical reactions to three-dimensional networks. Examples of such polymers are polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-propylene-dicyclopentadiene terpolymers, polybutadiene, natural rubber, polyamides, polyvinyl alkyl ethers, styrene copolymers such as styrene-butadiene-rubber, vinyl chloride copolymers such as vinyl chloride-vinyl acetate copolymers, ethylenevinyl acetate copolymers, polyesters or unsaturated polyesters, or mixtures of these polymers. The new copolymers are found to have an especially good adhesivizing action in the case of unsaturated polyester compositions, especially when they are used together with copolymerizable solvents. The acid component of the polyester can in this case consist of unsaturated dicarboxylic acids such as fumaric acid, maleic acid, maleic acid anhydride, itaconic acid, and additional saturated dicarboxylic acids such as phthalic acid, isophthalic acid, adipic acid etc. The alcohol component includes bifunctional alcohols such as ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, neopentyl glycol etc. Suitable copolymerizable solvents are, for example, styrene, diallyl phthalate, acrylic acid tert.-butyl ester. The polymerizable solvents can amount to as much as 60% of the polyester solution. The fillers, pigments or dyes with which the polymers can be bonded if the claimed new adhesivizers are used include inorganic oxide materials, such as silicon dioxide-containing substances, metals and metal alloys and metal oxides. Examples of substances containing silicon dioxide are glass, quartz, ceramic, sand, brick or tile, asbestos, and clay. In such bonds, suitable metals are principally aluminum, zinc, tin, magnesium, silver and nickel as well as metal alloys such as steel, chromium nickel, bronze, or also metals which have been subjected to a surface treatment with, for example, phosphates. The metal oxides include, for example, aluminum oxide, zinc oxide, titanium oxide, iron oxide and chromium oxide.
The preparation of the bond, between a polymer and the above-named inorganic oxide materials with the aid of an adhesivizer of the invention is performed in a manner known in itself, such as the one described, for example, in German Pat. No. 1,270,716.